Let's give a big ovation for Google!:
http://www.catholic.org/saints/patron.php?letter=A
Thomas More is the Patron Saint of politicians (which do need all the help they can get to enter Heaven)
I didn't know - but even without any web search T.M. came to my mind when reading the challenge.
The first thing we need is the Pope's approval of democracy in general.
In OTL, the French revolution and subsequent expansion brought forward
simultaneously
democracy, personal liberties and an atheistical philosophy.
So we have to take these apart.
Let's build an 18th century (I guess such a PoD timing is allowed) where
the monarchs of Europe gradually lose their Christian beliefs, for a bunch of reasons:
a) weariness with pointless religious quarrels between Protestants and Catholics,
and the tacid convention to elide these in many circumstances,
b) influence of Enlightenment philosophers and poets,
c) fading Ottomanian threats, which somewhat upheld Christian solidarity and identification.
This certainly has also happened in OTL to some degree.
But now they
openly confess so.
We could start by Louis XIV. of France claiming not being king by grace of God,
but by his own splendor - set into power by some impersonal provision.
Other absolutistic rulers will follow that fashion, esp. in non-Habsburg Germany
and Spain.
The various Popes regularly rant about these developments,
but some also get acquainted to the new situation.
After almost a century of godless megalomania,
the French revolution wipes away the old system of self-complacent tyrants.
Being ignited mostly by growing poverty under royal shadows and
by sufferance of martial consequences,
the rebellion claims to restitute the holy order of Europe,
which is designated as a country for Christ.
The menacing speeches against the rich from the Gospel of Luke and
the Epistle of Judas constitute their favorite slogans.
The current Pope, Clement XV., whose energetic advocacy for the return to Christianity
is hardly explicable given the facts,
finally has his great day. After their overthrow of the Ancien Regime,
he receives a delegation of the revolutionaries and welcomes them
as the legitimate lords of France. Among them there is the popular Abbé Sieyès,
who had opposed the royal policies for a long time.
Seeing that the young French republic keeps to its Christianity - despite all other political
issues - and that religion does not become any more popular on the thrones of Europe,
the subsequent Popes embark on appreciation of democracy as the preffered form of state.
In 1850, hardly two decades after his death, Abbé Sieyès is proclaimed Saint.
He becomes especially popular in France and in the duchies of
Germany liberated by French
conquests which had had particulary atheistical-absolutistic rulers
(i.e. all aristocratic lay states but Austria).
How many points does that score?